The role of SLNB in the management of soft tissue sarcoma has yet to be defined [8, 9, 13]. In our institution it is current practice to undertake SLNB in patients with epithelioid sarcoma given the relatively high rate of lymph node metastasis in these tumours. Previous studies have reported that the incidence of lymph node metastasis in such tumours is between 16.7 and 80% [5, 10, 11]. A positive SLNB in these cases is followed by a formal lymph node dissection. A number of soft tissue sarcomas, such as rhabdomyosarcoma, clear cell sarcoma and synovial sarcoma, have also been shown to have a propensity for regional lymph node metastasis and some observers have suggested that SLNB may be of prognostic benefit in these tumours . Previous estimates of the incidence of lymph node metastasis in all patients with leiomyosarcoma have been between 2.7 and 10.6%. [510H] These studies examined the metastatic rate of leiomyosarcomas arising at several different sites collectively and not just that of leiomyosarcomas of deep soft tissues of the extremities. In the present study we found that the rate of lymph node metastasis in extremity deep soft tissue leiomyosarcomas to be 7%.
In patients with intermediate thickness melanoma, SLNB has become widely accepted as a minimally invasive method of staging the regional lymph nodes [14, 15]. When SLNB is performed in these patients, 20% will be found to have micrometastasis. However when SLNB is performed in thin melanomas, with a Breslow thickness less than I mm, the micrometastasis rate falls to 5% . Current AJCC guidelines do not recommend routine use of SLNB in this group [17, 18], and on this basis the comparable rate of lymph node metastasis in deep soft tissue leiomyosarcomas would not appear to justify the extra morbidity (eg extra operating time, potential wound problems) associated with undertaking SLNB.
Recent work at our institution has shown that soft tissue sarcomas with a high propensity to metastasise to lymph nodes contain intratumoural lymphatics ; intratumoural lymphatics were found to be present in all epithelioid sarcomas and a number of other sarcomas including leiomyosarcoma. Lymph node metastasis has been reported in up to 80% of epithelioid sarcomas [5, 10, 11]. The lower incidence of lymph node metastasis in leiomyosarcomas may reflect the fact that intratumoural lymphatics are found less commonly in these tumours. It is none the less significant that in our study the two leiomyoarcomas which did metastasise to regional lymph nodes both contained intratumoural lymphatics. Immunohistochemical demonstration of lymphatic vessels in these primary leiomysarcomas was of prognostic significance with regard to the development of lymph node metastasis, and it could be argued that SLNB is indicated in primary leiomyosarcomas of the extremities where intratumoural lymphatics are identified.
We found a high rate of local recurrence in extremity deep soft tissue leiomyosarcoma patients with 25.9% experiencing recurrence despite adequate resection and adjuvant radiotherapy. Mankin and Hornicek report a recurrence rate of 10.8% in 65 patients with leiomyosarcoma . Again this study did not differentiate between leiomyosarcoma of the extremities and other sites. The findings of the present study indicate that deep soft tissue leiomyosarcoma of the extremities, in contrast to leiomyosarcoma arising at other sites has a greater propensity to local recurrence. Such recurrences are difficult to treat and surgical resection of an already irradiated area remains the only option.